1. Field of the Invention
The present invention relates to a method for searching services, resources and/or functionalities in a network wherein the network comprises a multitude of nodes to which routable network addresses are assigned, and wherein the services, resources and/or functionalities which are to be searched, are specified by a source node.
2. Description of the Related Art
Methods of the mentioned kind have been state of the art for some time. With reference to an increasing trend to provide special services, resources and/or functionalities such as, for example, firewalls, data storage, media cache, transcoder etc. more and more on the network side, such methods steadily gain a growing importance.
In the framework of a concrete generic method, it is common to register available services or resources at a commonly known directory service. (See E. Guttman, C. Perkins, J. Veizades, M. Day, Service Location Protocol, Version 2, Internet RFC2608, 1999, and J. Hodges, R. Morgan, Lightweight Directory Access Protocol (v3): Technical Specification, Internet RFC3377.) Clients or nodes, respectively, searching for specific services/resources query directly this directory service. The disadvantage of this approach is that the continuous updating of the directory service is extremely cost-intensive. This is specifically the case in highly dynamic and/or mobile environments. The number of update requests that is necessary in order to keep the directory service up to date increases very much, in particular if the availability of a service or specific information needed for using a service changes often. The same is valid in case the node offering a service is a mobile node.
Another disadvantage going along with the use of a directory service is that a directory based service typically is not able to take into account topological aspects, i.e. in particular the location of a resource or a service within the network.
In another known approach, a “lookup” request is broadcasted into the network when looking for specific network-side services and/or resources. (See K. S. Lim, R. Stadler, “A Navigation Pattern for Scalable Internet Management”, Seventh IFIP/IEEE International Symposium on Integrated Network Management (IM2001), Seattle, USA, May 2001, pp. 405-420). Nodes which are able and ready to provide the requested service or the requested resource, reply to this lookup request. This method is also called “flooding”.
The significant disadvantage of this method is that it does not scale. In large networks the described approach causes an enormous amount of superfluous traffic and potentially a very high number of replies. Without a corresponding indication at which location within the network a requested service should be, such a search has impact on all the nodes of a network.